To cope with the diversification of radio access technologies (RATs), 3GPP (3rd Generation Partnership Project) specifies handovers between RATs standardized by 3GPP, for example, a handover between UTRAN (UMTS Terrestrial Radio Access Network) and E-UTRAN (Evolved UTRAN) and a handover between E-UTRAN and GERAN (GSM/EDGE Radio Access Network) (see Non Patent Literature 1). Further, 3GPP has studied handovers between the RATs standardized by 3GPP and other RATs (non-3GPP RATs) (see Non Patent Literature 2). Specific examples of the non-3GPP RATs include a wireless LAN standardized by IEEE802.11, WiMAX (Worldwide Interoperability for Microwave Access) standardized by IEEE 802.16, and cdma2000 standardized by 3GPP2 (3rd Generation Partnership Project 2).
FIG. 14 is a diagram showing a network configuration example in the case of connecting a mobile station to a core network (EPC (Evolved Packet Core)) of 3GPP via a plurality of RATs, which has been studied by 3GPP. Referring to FIG. 14, a mobile station (UE) 4 supports a plurality of RATs including E-UTRAN, UTRAN, and a non-3GPP RAT. A base station (eNB) 11 supports E-UTRAN specified by 3GPP, generates an E-UTRAN cell 10, and is connected to the mobile station (UE) 4. The base station (eNB) 11 relays user data between an EPC 40 and the mobile station 4.
The EPC 40 is a core network corresponding to E-UTRAN specified by 3GPP. The EPC 40 includes an S-GW (Serving Gateway) 41, a P-GW (Packet Data Network Gateway) 42, and an MME (Mobility Management Entity) 43. The S-GW 41 and the P-GW 42 are transfer nodes that transfer user data. The P-GW 42 functions as a gateway to an external network 70, and terminates a communication path (i.e. an EPS (Evolved Packet System) bearer) between the mobile station 4 and the EPC 40. The external network 70 is called PDN (Protocol Data Network) in 3GPP. The MME 43 performs mobility management and bearer management for the mobile station (UE) 4. The bearer management performed by the MME 43 includes management of information (such as a QoS class, a bearer ID, and bearer path information) relating to a configuration of the communication path (i.e. the EPS bearer) between the mobile station (UE) 4 and the P-GW 42, and signaling for bearer setup to the base station (eNB) 11, the mobile station (UE) 4, the S-GW 41, and the like.
A base station (NB) 21 supports UTRAN specified by 3GPP, generates a UTRAN cell 20, and is connected to the mobile station (UE) 4. The base station (NB) 21 relays user data between the mobile station 4 and an upstream network including an RNC (Radio Network Controller) 22 and a GPRS packet core 50. The RNC 22 is a node that performs radio resource management for the UTRAN including the base station (NB) 21.
The GPRS packet core 50 is a core network corresponding to UTRAN specified by 3GPP. The GPRS packet core 50 includes an SGSN (Serving GPRS Support Node) 51 serving as a control node and a transfer node. The SGSN 51 performs mobility management and bearer management for the mobile station (UE) 4, and performs processing of transferring user data. Uplink user data transmitted from the mobile station (UE) 4 belonging to the base station (NB) 21 is transferred to the EPC 40 via the RNC 22 and the SGSN 51, and is transferred to the external network 70 via the P-GW 42. Downlink user data is also transferred via the EPC 40 and the GPRS packet core 50 in the same manner as the uplink user data.
A base station (AP (Access Point)) 31 supports a non-3GPP RAT, such as cdma2000, WiMAX, or a wireless LAN, generates a non-3GPP cell 30, and is connected to the mobile station (UE) 4. The base station (AP) 31 relays user data between a non-3GPP upstream network 60 and the mobile station 4.
An HLR (Home Location Register)/HSS (Home Subscriber Server) 44 manages an identifier, authentication information, positional information, and the like of the mobile station (UE) 4. The HLR/HSS 44 collaborates with the MME 43 and the SGSN 51, and performs authentication processing when the mobile station (UE) 4 attaches to the EPC 40 and the GPRS packet core 50.
The non-3GPP upstream network 60 is an upstream network corresponding to the non-3GPP RAT supported by the base station (AP) 31. The non-3GPP upstream network 60 includes a transfer node 61 that transfers user data, and a control node 62 that performs, for example, bearer management and mobility management. Uplink user data transmitted from the mobile station (UE) 4 belonging to the base station (AP) 31 is transferred to the EPC 40 via the transfer node 61, and is transferred to the external network 70 via the P-GW 42. Downlink user data is also transferred via the EPC 40 and the non-3GPP upstream network 60 in the same manner as the uplink user data.
The non-3GPP upstream network 60 includes a RAN node and a core network node. In the case of WiMAX, the non-3GPP upstream network 60 includes, for example, an ASN GW (Access Network Gateway) disposed in a radio access network (WiMAX Access Service Network (ASN), and a HA (Home Agent) disposed in a core network (Core Services Network (CSN)). Each of the ASN GW and the HA corresponds to both the transfer node 61 and the control node 62.
As described above, in the architecture shown in FIG. 14, user data transmitted and received between the external network 70 and the mobile station 4 is transferred via the P-GW 42 disposed in the EPC 40. In other words, in the architecture shown in FIG. 14, the P-GW 42 disposed in the EPC 40 operates as an anchor node when the mobile station (UE) 4 performs a handover between the base stations 11, 21, and 31 which support different RATs.